The present invention relates to new and improved odor-control system to enhance conditions in high-rise animal rearing facilities. More particularly, it relates to apparatus and methods that employ alum to control the chemical composition of the atmosphere in the animal rearing levels of a high-rise rearing facility.
One of the predominant systems currently used for egg production from laying hens involves growing the birds in cages on the second floor of a two story animal rearing facility referred to as a high-rise laying hen house. In these houses, the manure from the birds falls from the second floor to the first floor where it accumulates. After a period of time, the manure is removed from the house and applied to the land as an agricultural fertilizer.
Accumulation of manure in animal rearing facilities results in the production of ammonia gas, which can be produced in relatively high quantities. For over thirty years, researchers have known that buildup of ammonia levels in animal rearing facilities adversely affects poultry and other animals. Research on the effects of ammonia on poultry has shown that it causes decreased growth rates, reduced feed efficiency, decreased egg production, damage to the respiratory tract, increased susceptibility to New castle disease, increased incidence of airsaculitis, increased levels of Mycoplasma gallisepticum, and increased incidence of keratoconjunctivitis. For these reasons, it is now recommended that 25 ppm ammonia should not be exceeded in poultry houses.
Ammonia volatilization from poultry litter has also been shown to be detrimental to the environment due to its effect on acid atmospheric deposition. Ammonia plays a key role in acid rain production and the dominant source of atmospheric ammonia in Europe was found to be livestock wastes, with long-term trends showing a 50% increase in ammonia emissions in Europe from 1950-1980. Ammonia raises the PH of rainwater, which allows more SO.sub.2 to dissolve in it, eventually forming ammonium sulfate, which releases nitric and sulfuric acid in soils upon oxidation. Ammonia volatilization also greatly increases atmospheric N fallout, which contributes to eutrophication. N deposition from wet fallout tripled from 1955 to 1980 and corresponded with N losses from agriculture during this same period. Atmospheric ammonia can also result in the formation of ammonium nitrate particles in the air. These particles, which are usually less than two microns in size, contribute greatly to small airborne particle pollution referred to as PM.sub.10 's (particulate matter less than 10 microns).
Another environmental problem currently facing the poultry industry is phosphorus runoff from fields receiving poultry manure as an agricultural fertilizer. Phosphorus is considered to be the primary element of concern with respect to eutrophication of fresh water systems. Recent studies have shown extremely high phosphorus concentrations in the runoff water from pastures receiving low to moderate levels of poultry manure as fertilizer. The majority (80-90%) of the phosphorus in the runoff water is dissolved reactive P, which is the form that is more readily available for algal uptake. The threat of eutrophication due to phosphorus runoff has results in limits being placed on the number of animals which may be produced per area of land in the Netherlands.
Similar problems are encountered with manure deposited in other facilities in which other animals, such as poultry breeding stock, are reared in a raised facility.
Accordingly, new facilities and methods are needed for rearing animals under conditions which reduce ammonia volatilization, prevent nitrogen losses to improve the fertilizer value of manure to be used as an agricultural fertilizer and to reduce the soluble phosphorus content of the manure to prevent phosphorus runoff from fields fertilized with poultry manure agricultural fertilizers.